In optical transmission devices such as optical add/drop multiplexers suitably employed in an optical communication system, there is recent demand to make nodes multifunctional in order to build photonic networks. Rather than just point-to-point transmission, there is demand for functionality to freely switch an optical signal path such as optical add/drop multiplexing (OADM) and wavelength cross-connect (WXC) functionality.
There are the following 3 examples of functions being demanded from now on for optical add/drop multiplexers. One is for a colorless function, enabling freely selected wavelengths to be added/dropped. Another is a directionless function, enabling insertion (add)/splitting (drop) to a freely selected path. Yet another is a contentionless function, enabling identical wavelengths to be added/dropped without collision. These three functions (colorless, directionless, contentionless (CDC)) are expected to contribute to improving the efficiency of networks (wavelength routing), making the placement of devices more flexible (saving space by reducing device slots), and reducing cost.